I've just run in to an annoying feature - the [show_if][debug_status] of the menu items gets written in to the save files, and then causes WML errors if given to someone who doesn't have the add-on installed.

In trait definitions one sets all three statuses, but to not break with abilities and alike which have not been rewritten to check for one of the three instead, non_living is set as well for compatibility.
The Feeding ability for example checks for unplaguable now.

Basically not_living is or should be deprecated and exists only to keep compatibility to code which has not been rewritten yet. It's more an alias than a proper status.